some info. from Deora Aille, recording of Máire Aine Ní Dhonnchadha, Ceirníní Claddaigh (Claddagh Records), about the song "Sagart O Dónaill": although the song is known in every Gaeltacht (Irish-speaking) area of Ireland, it's thought to originate in Donegal, where the priest is known by his first name. One of the verses begins "Crádh ort, a Dhoimnic Uí Dhónaill" - a plague on you, Dominic O Dónaill.

"Dominic is said to have become a Protestant minister at Downings near Carrigart, County Donegal, and his tomb in the Protestant churchyard at Carrigart is inscribed:
'In memory of Rev. Dominck O'Donell who departed this life 1793 aged 93 years'."

Einrí O Muirgheasa, compiler of "Dhá Céad de Cheoltaí Uladh", gives the probable date of this song as 1740-50. I'll get back to you when I have a chance to read through O Muirgheasa's notes and see if there is any further detail.